#一、计算器
#if-elif
#计算器进行基础运算
first=float(input("请输入第一个数："))
second=float(input("请输入第二个数："))
operator=input("请输入运算符：+ - * / :")
if operator == '+':
    print(first + second)
elif operator =='-':
    print(first -second)
elif operator =='*':
    print(first * second)
elif operator =='/':
    if second ==0:
        print("除数不能为0")
    else:
        print(first / second)
